This invention relates to an improved combustible fuel and oxygen burner, wherein the combustible fuel and the oxygen are mixed within a mixing chamber, ignited within a surrounding second ignition chamber and the resulting hot gases from the ignited mixture expelled outwardly from the ignition chamber.
This invention is an improvement over my earlier disclosure in U.S. patent application Ser. No. 5,348,469, which issued Sep. 20, 1994, titled, Air, Propane and Oxygen Burner With No Exit Flame.
The use of combining a fuel in gaseous form with compressed air or oxygen under pressure to increase the temperature has long been fraught with concerns, among which are those regarding the complexity of controlling the gas mixture, and the difficulty in controlling the exit flame length from the combustion of the fuel.
The present fuel and oxygen burner described herein overcomes these concerns and provides for a fuel/oxygen mixing mechanism which achieves an optimized burn rate. Further, the mixing mechanism ensures combustion takes place internally of the burner so that only heated gases are exhausted from the burner thereby eliminating exit flame.
The present invention relates to an improved burner which mixes fuel and oxygen or air within in a mixing chamber in the burner. The resulting mixture is ignited within a separate ignition chamber which surrounds the mixing chamber to produce hot gases which are then expelled outwardly from the ignition chamber.
The burner ignition chamber is a hollow tube closed at one end by a plug. The plug is hereinafter alternatively referred to as a cylindrical body section. The cylindrical body section has a bore formed at one end, coaxially with the longitudinal axis of symmetry of the cylindrical body section. The bore extends part way into cylindrical body section and terminates short of the exposed end (the first end) of the cylindrical body section, which is generally co-terminal with one end (the corresponding first end) of the hollow tube, in a radially enlarged plenum chamber. The mixing chamber is formed by insertion of a second smaller diameter tube into the plenum so as to also be coaxial with the longitudinal axis of the cylindrical body section and the hollow tube forming the ignition chamber. The cylindrical body section may have a radially extending shoulder adjacent the co-terminal end of the hollow tube.
The first end of the cylindrical body section incorporates a pair of drilled and threaded passageways. A first passageway serves as an inlet port for a source of combustible fuel. It is located coaxially of the cylindrical body section and extends axially into open communication with the plenum chamber. The second passageway serves as an inlet port for a source of compressed air or oxygen. It is located radially outwardly of, so as to extend parallel to, the first passageway (i.e. radially outwardly relative to the longitudinal axis of the hollow tube), and extends axially a distance sufficient to bring an end of the second passageway into open communication with the plenum chamber.
A diffuser is mounted within the bore of the mixing chamber. The diffuser has a longitudinally extending small diameter axial bore hole, an externally threaded shaft portion, a shoulder portion and a pair of oppositely disposed conically shaped adjacent faces forming a rhombus in cross-section along the bore. The bore hole communicates fuel along the threaded shaft portion, which threads into the first passageway. The convergence of the conically shaped faces forms an annular apex that is only slightly smaller in diameter than the internal diameter of the axial bore of the mixing chamber.
A plurality of slit-like skewed passages are formed equidistantly around the periphery or rim of the annular apex of the diffuser. These slit-like passages may be generally inclined at 30 degrees relative to the longitudinal axis of the mixing chamber.
The mixing chamber is formed within a mixing tube. The mixing tube is mounted in the plenum by being slidably inserted into the axial bore of cylindrical body section, so as to slip over the diffuser. The annular apex of the diffuser snugly fits inside of the mixing tube. The mixing tube has diametrically opposed xe2x80x9cVxe2x80x9d-shaped notches formed in the end of the mixing tube which is seated in the plenum chamber. The notches are radially offset about the longitudinal axis of the hollow tube relative to the second passageway. The opening of the second passageway into the plenum may be bisected by one edge of the two edges extending between the xe2x80x9cVxe2x80x9d-shaped notches. The notched end of the mixing tube is placed into firm contact with the inner surface of the plenum chamber, thereby allowing open fluid communication between the interior of the mixing tube and the plenum chamber. Oxygen or air under pressure can then pass from the compressed air passageway (the second passageway) through the plenum chamber into the mixing tube, upstream of the annular apex of the diffuser, i.e. between the apex of the diffuser and the plenum chamber. Contact of the flow of oxygen or air with the first or upstream conically shaped face of the diffuser forces the flow toward the side walls of the mixing tube and through the plurality of skewed passages around the annular apex of the diffuser.
The flow of combustible fuel passes through the longitudinal bore hole of the diffuser into the mixing tube downstream of the diffuser. Once it exits the bore hole it diverges in a divergent stream toward the side walls of the mixing tube. Mixing of the combustible fuel with the oxygen or air exiting from the skewed passages takes place in the mixing tube downstream of the diffuser in the interaction between the two flows, namely between the diverging flow of combustible fuel and the swirling flow of air or oxygen.
As the mixture exits the mixing tube the mixture is ignited for complete combustion within the ignition chamber by any appropriate conventional means.
In summary, the no exit-flame burner of the present invention includes nested elongate mixing and ignition chambers formed in tubes. The ignition chamber tube has a longitudinal axis. The mixing chamber tube is of shorter length than said ignition chamber tube and is nested coaxially along said longitudinal axis so as to nest a first end of said mixing chamber tube in a first end of said ignition chamber tube. In use the burner provides an efficient burn so only heated exhaust gases exit the ignition tube, giving directional control for use of the heat on what may be a small area.
The first ends of the ignition and mixing chamber tubes are sealed by a sealing member. A gas port for delivery of oxygen-bearing gas is formed in the sealing member, positioned radially outwardly of the longitudinal axis.
A gas diffuser is mounted at an upstream end of the diffuser to the sealing member. The diffuser is nested coaxially within the mixing chamber tube, a fuel-feeding bore within the gas diffuser aligned coaxially with the longitudinal axis at an exit orifice of the bore within the mixing chamber tube. The bore communicates in fluid communication with a fuel-feeding infeed mounted on the sealing member.
The gas diffuser, at a downstream end opposite the upstream end, is shaped generally as a rhombus in cross-section along the longitudinal axis to thereby define a rim around an apex thereof. The rim is orthogonal to the longitudinal axis and sized to extend substantially around, closely adjacent to, a corresponding inside surface of the mixing chamber tube to thereby define an upstream gas plenum upstream of the rim between the rim and the sealing member.
A radially spaced apart array of flow-directing slits are formed in the rim. They are radially spaced apart around the longitudinal axis. The slits direct a gas flow from the plenum into adjacency to the exit orifice of the bore in the mixing chamber tube downstream of the rim. The slits in the array of flow-directing slits may be skewed from a downstream flow direction parallel to the longitudinal axis. In particular, the slits may be skewed by a skew angle of, for example 30 degrees, so as to impart a counter-clockwise swirl to the gas flow when viewed from downstream along the gas flow.
In one embodiment the tubes are cylindrical, and the diffuser defines a pair of opposed facing frusto-conical surfaces intersecting at the rim. The frusto-conical surfaces may define included angles of 45 degrees between the surfaces and the longitudinal axis.
The sealing member may be a solid plug having a mixing tube bore therein, where the mixing tube bore is coaxial with the longitudinal axis and sized to snugly hold the mixing chamber tube therein. A radially expanded annular plenum may be formed in an upstream end of the receiving bore in fluid communication with the gas port.
A perimeter portion of an upstream end of the mixing chamber tube may bisect the gas port, and the upstream end of the mixing chamber tube may abut an interior upstream surface of the plenum. The perimeter portion may be notched.